1. Technical Field
The invention relates to fifth wheel assemblies for coupling trailers to tractors and more particularly to a power actuated air release mechanism for moving the king pin locking mechanism from locked to the unlocked position. Even more particularly the invention relates to a power-actuated unlocking mechanism having a safety latch incorporated therein to assist in securing the locking mechanism in the locked position.
2. Background Information
Large highway freight trailers are usually coupled to an associated tractor by means of a fifth wheel assembly. These fifth wheel assemblies have a top plate with a generally V-shaped opening through which a king pin of the trailer moves where it is secured to the fifth wheel by some type of locking mechanism. One type of locking mechanism is a C-shaped jaw which pivots from an open position to a closed position after the king pin is received therein. Various mechanisms have been provided for moving the locking jaw between open and closed positions and for retaining the jaw in either the open or closed position. Most of these mechanisms require the operator of the vehicle to manually manipulate one or more levers on the fifth wheel assembly prior to uncoupling the tractor and trailer from each other. Some of these fifth wheel assemblies use a pressure actuated cylinder to facilitate the unlocking of the locking jaw from the king pin. Some examples of these prior art fifth wheel locking mechanisms and power actuated releases therefor are shown in U. S. Pat. No. 5,028,067, 5,176,396 and 5,472,223.
One problem that exists with many existing fifth wheel assemblies is to couple and uncouple the trailer and tractor without requiring any manual manipulation at the fifth wheel by the operator yet provide for a secure latching of the locking jaw with the king pin, and in which the locking mechanism can not prematurely move to the unlocked position due to road vibration and especially in the event of an accident where severe forces are applied in various directions to the coupling between the tractor and trailer.
The present invention provides a fifth wheel assembly which uses a pressure actuated cylinder operated by the vehicle driver from within the tractor for moving the locking mechanism from the locked to the unlocked position without requiring any manual manipulation of the locking mechanism by the operator at the fifth wheel assembly location.
Another aspect of the invention preferably provides a safety latch which assists in securing the locking mechanism in its locked position and prevents movement of the locking mechanism toward the unlocked position.
Still another feature of the invention is the ability to provide the power actuated unlocking mechanism and safety latch mechanism as a retrofitted item or kit for mounting on an existing fifth wheel assembly avoiding the necessity of replacing the entire fifth wheel to secure the advantages of the present invention.
A feature of the invention is positioning of the power actuated unlocking mechanism and associated safety latch mechanism beneath the top surface of the top plate where it is out of contact with the trailer thereby avoiding damage and which is provided with adjustment bolts to adjust the locking mechanism and safety mechanism in the desired position to compensate for manufacturing and assembly tolerances.
Still another aspect of the invention is the reduced reliance on springs which are subject to change in force to retain the locking mechanism in the locked and unlocked positions and to secure the safety latch mechanism in engagement with the unlocking mechanisms in the locked and unlocked positions.